In nature, living cells divide and interconnect in the formation of complex biological systems creating structure-function hierarchies that span from nanometer to meter scales. This bottom-up approach leverages genetic programming and environmental stimuli to direct cellular self-assembly and organogenesis into specialized tissues and organs. Capabilities, including the parallel processing of neural networks, the combination of force, strain and efficiency of striated muscle, and the immune response to pathogens, far exceed what can be achieved in manmade systems. Learning to use living cells as an integral building block in manmade, synthetic systems thus portends the ability to create classes of hybrid devices that combine the advantages of biological and engineering grade materials.
Efforts to build biosynthetic materials or engineered tissues that recapitulate these structure-function relationships often fail because of the inability to replicate the in vivo conditions that coax this behavior from ensembles of cells. For example, engineering a functional muscle tissue requires that the sarcomere and myofibrillogenesis be controlled at the micron length scale, while cellular alignment and formation of the continuous tissue require organizational cues over the millimeter to centimeter length scale. Thus, to build a functional biosynthetic material, the biotic-abiotic interface must contain the chemical and/or mechanical and/or physical properties that support multiscale coupling.
Multiscale coupling of properties over several length scales within a functional biosynthetic material often requires the anisotropic arrangement of hierarchical structures within that material. In the muscle tissue example, anisotropic arrangement of sarcomeres and muscle cells in striated muscle tissue concentrate contraction force along defined axes to effectuate coordinated movements of the skeleton. Methods to produce anisotropic arrangement of hierarchical structures are therefore desirable to focus particular properties of the material. Such methods could be used to control development of biotic tissue in association with an abiotic medium or substrate to produce an anisotropic environment, analogous to muscle attachment to bone.